The repeal of prohibition by the 21st Amendment on Dec. 5, 1933 allowed each state to set its own alcohol consumption laws. At that time, most states established the minimum legal drinking age (MLDA) for alcohol at 21 years of age. Following the July 1, 1971 passage of the 26th Amendment, which lowered the legal voting age from 21 to 18 years of age, 30 US states lowered their MLDA to 18, 19, or 20; by 1982, only 14 states still had an MLDA of 21.

The enactment of the National Minimum Drinking Age Act of 1984 (56 KB) prompted states to raise their legal age for purchase or public possession of alcohol to 21 or risk losing millions in federal highway funds. By 1988, all 50 states had raised their MLDA to 21.

California (1933) and Oregon (1933) have the nation's oldest MLDA 21 laws while South Dakota (Apr. 1, 1988) and Wyoming (July 1, 1988) have the most recent MLDA 21 laws.

The charts below show the date on which the MLDA 21 laws became effective in each state.